Unifdef TM_GMTOFF TM_ZONE USG_COMPAT ALTZONE to make the code more readable.
No binary change when compiled with -g0.
Note that wcsftime.c did not even compile without TM_ZONE.
OK millert@

- register int idays; /* unsigned would be so 2003 */
+ int idays; /* unsigned would be so 2003 */

register is so 1973

the one true type of time_t is a signed integer

move include lines around a bit

enh@google reported a warning in crufty y2k code. just delete it.
ok deraadt stsp

Properly handle "%%" and "%N" where N is not a supported escape.
This is consistent with strftime(3) behavior. OK stsp@

put in code for wcstfime, as discussed with millert@ and stsp@ (and tested
by ajacoutot@, thx), to be linked in and activated alongside wscanf...